Motor drive cooling duct system and method

ABSTRACT

The present invention relates generally to tuning the flow of cooling air across converter and inverter heat sinks in a motor drive system. More specifically, present techniques relate to motor drive duct systems having parallel cooling air duct channels dedicated to providing cooling air for a converter heat sink and an inverter heat sink, respectively. In particular, a first duct channel through an inverter duct and a converter duct is dedicated to providing cooling air to the converter heat sink without cooling the inverter heat sink, whereas a second duct channel through the inverter duct and the converter duct is dedicated to providing cooling air to the inverter heat sink without cooling the converter heat sink.

BACKGROUND

The present invention relates generally to the field of power electronicdevices such as those used in power conversion or applying power tomotors and similar loads. More particularly, the invention relates to amotor drive cooling duct system having optimized cooling air flow paths.

In the field of power electronic devices, a wide range of circuitry isknown and currently available for converting, producing, and applyingpower to loads. Depending upon the application, such circuitry mayconvert incoming power from one form to another as needed by the load.In a typical arrangement, for example, constant (or varying) frequencyalternating current power (such as from a utility grid or generator) isconverted to controlled frequency alternating current power to drivemotors, and other loads. In this type of application, the frequency ofthe output power can be regulated to control the speed of the motor orother device. Many other applications exist, however, for powerelectronic circuits which can convert alternating current power todirect current power (or vice versa) or that otherwise manipulate,filter, or modify electric signals for powering a load. Circuits of thistype generally include rectifiers (converters), inverters, and similarswitched circuitry. For example, a motor drive will typically include arectifier that converts AC power to DC. Power conditioning circuits,such as capacitors and/or inductors, are often employed to removeunwanted voltage ripple on the internal DC bus. Inverter circuitry canthen convert the DC signal into an AC signal of a particular voltage andfrequency desired for driving a motor at a particular speed or torque.The inverter circuitry typically includes several high powersemiconductor devices, such as insulated-gate bipolar transistors(IGBTs), silicon controlled rectifiers (SCRs) and diodes controlled bydrive circuitry.

The power semiconductors detailed above will typically generatesubstantial amounts of heat, which must be dissipated to avoid damagingheat sensitive electronics. Typically, therefore, some form of coolingmechanism may be employed to enhance heat extraction and dissipation.Often, the circuitry is packaged together as a unit with a built-incooling channel that provides cool air to several components. It is nowrecognized that, because the air within the channel is heated as ittravels through the channel, components near the exhaust end of the airchannel will usually experience a diminished cooling effect. Therefore,as packaged control units become more compact, the need for efficientheat dissipation becomes more critical. Additionally, as the workload ormotor speed changes, the temperature of the semiconductors generallyincreases, causing higher failure rates and reduced reliability. Theoutput of the unit is often, therefore, limited by the maximumtemperature that the unit can handle without substantially increasingthe risk of failure. A more effective cooling mechanism would,therefore, allow the motor drive to operate at higher motor powerlevels. Therefore, it may be advantageous to provide a motor drive withan improved cooling mechanism. In particular, it may be advantageous toprovide a cooling mechanism which provides a reduced air flow resistanceand increased air flow while maintaining a high level of thermalperformance.

BRIEF DESCRIPTION

The present invention relates generally to tuning the flow of coolingair across converter and inverter heat sinks in a motor drive system.More specifically, present techniques relate to motor drive duct systemshaving parallel cooling air duct channels dedicated to providing coolingair for a converter heat sink and an inverter heat sink, respectively.In particular, a first duct channel through an inverter duct and aconverter duct is dedicated to providing cooling air to the converterheat sink without cooling the inverter heat sink, whereas a second ductchannel through the inverter duct and the converter duct is dedicated toproviding cooling air to the inverter heat sink without cooling theconverter heat sink. A guide vane adjacent to the inverter duct maycontrol the flow of cooling air from a blower between the first andsecond duct channels. In addition, the inverter duct and the converterduct may both include baffled walls that direct cooling air into contactwith the inverter heat sink and the converter heat sink, respectively,such that temperature gradients across the heat sinks are minimized.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical representation of an exemplary embodiment ofa motor drive system;

FIG. 2 is further diagrammatical representation of a portion of themotor drive system of FIG. 1 illustrating power layer interfacecircuitry used in the multiple parallel motor drives;

FIG. 3 is a perspective view of an exemplary embodiment of a cabinet,within which components of a motor drive may be housed;

FIG. 4 is a schematic diagram of an exemplary embodiment of a motordrive duct system, which includes an inverter duct, a converter duct,and an exhaust duct;

FIG. 5 is a perspective view of an exemplary embodiment of the converterduct when extracted from the cabinet of FIG. 3;

FIG. 6 is a perspective view of an exemplary embodiment of the inverterduct when extracted from the cabinet of FIG. 3;

FIG. 7 is a perspective exploded view of an exemplary embodiment of theinverter duct, converter duct, inlet duct, and exhaust duct;

FIG. 8 is a side exploded view of an exemplary embodiment of theinverter duct, converter duct, inlet duct, and exhaust duct;

FIG. 9 is a partial perspective view of an exemplary embodiment of theinverter duct and the converter duct when detached from each other;

FIG. 10 is a partial perspective view of an exemplary embodiment of theinverter duct and the converter duct when attached to each other;

FIG. 11 is a partial perspective view of an exemplary embodiment of theexhaust duct, the converter duct, and the inverter duct;

FIG. 12 is a front view of an exemplary embodiment of the inverter duct;

FIG. 13 is a cross-sectional side view of an exemplary embodiment of thesecond inverter duct channel of the inverter duct;

FIG. 14 is a front view of an exemplary embodiment of the converterduct;

FIG. 15 is a cross-sectional side view of an exemplary embodiment of thefirst converter duct channel of the converter duct;

FIG. 16 is a conceptual side view of an exemplary embodiment of theinverter heat sink and the baffled wall of the inverter duct of FIG. 13;

FIG. 17 is a partial perspective view of an exemplary embodiment of theinverter duct and the inlet air duct; and

FIG. 18 is a partial cross-sectional side view of an exemplaryembodiment of the inverter duct and the inlet air duct.

DETAILED DESCRIPTION

Turning now to the drawings, FIG. 1 represents a drive system 10 inaccordance with aspects of the present disclosure. The drive system 10is configured to be coupled to a source of AC power, such as the powergrid, as indicated by reference numeral 12, and to deliver conditionedpower to a motor 14 or any other suitable load. The system 10 comprisesa plurality of individual drives coupled to one another in parallel toprovide power to the load. In the example illustrated in FIG. 1, forexample, a first drive 16 is illustrated as coupled to a second drive 18and a further drive 20 which may be the third, fourth, fifth, or anysuitable terminally numbered drive. A presently contemplated embodimentmay accommodate up to five parallel drives, although fewer or more maybe configured in the same way. It should be noted that certain aspectsof the techniques described herein may be used with a single drive.However, other aspects are particularly well-suited for multipleparallel drives.

A controller 22 is coupled to the circuitry of each drive and isconfigured to control operation of the circuitry as described more fullybelow. In a presently contemplated embodiment, the controller 22 may behoused in one of the drives or in a separate enclosure. Appropriatecabling (e.g., fiber optic cabling) is provided to communicate controland feedback signals between the controller 22 and the circuitry of theindividual drives. The controller 22 will coordinate operation of thedrives to ensure that the provision of power is shared and thatoperation of the drives is synchronized sufficiently to provide thedesired power output to the motor 14. In the embodiment illustrated inFIG. 1, power filtration circuitry 24 may be provided upstream of themotor drives. Such circuitry may be provided upstream of a line-side bus26 or similar circuitry may be provided downstream of the bus in each ofthe drives. Such circuitry may include inductors, capacitors, circuitbreakers, fuses, and so forth, that are generally conventional in designand application.

The power bus 26 distributes three phases of AC power between theindividual drives. Downstream of this bus, each drive includes convertercircuitry 28 that converts the three phases of AC power to DC power thatis applied to a DC bus 30. The converter circuitry 28 may be passive oractive. That is, in a presently contemplated embodiment, non-switchedcircuitry alone is used to define a full wave rectifier that convertsthe incoming AC power to DC power that is applied to the bus. In otherembodiments, the converter circuitry 28 may be active, includingcontrolled power electronic switches that are switched betweenconducting and non-conducting states to control the characteristics ofthe DC power applied to the bus.

Continuing with the components of each drive, bus filtration circuitry34 may be provided that conditions the DC power conveyed along the DCbusses 30. Such filtration circuitry may include, for example,capacitors, inductors (e.g., chokes), braking resistors, and so forth.In some embodiments, common devices may be provided on the DC busses,which may be coupled to one another by links illustrated by referencenumeral 32.

Each drive further includes inverter circuitry 36. As will beappreciated by those skilled in the art, such circuitry will typicallyinclude sets of power electronic switches, such as insulated gatebipolar transistors (IGBTs) and diodes arranged to allow for convertingthe DC power from the bus to controlled frequency AC output waveforms.The inverters thus create three phases of controlled frequency output,with each phase being shorted or combined along an output bus 38. Thecombined power may be applied to output filtration circuitry 40, whichmay include magnetic components that couple the output power between thephases. Such circuitry may also be provided along the load-side bus 38.

The controller 22 will typically include control circuitry 42 that isconfigured to implement various control regimes by properly signalingthe inverter circuitry 36 (and, where appropriate, the convertercircuitry 28) to control the power electronic switches within thesecircuits. The control circuitry 42 may, for example, include anysuitable processor, such as a microprocessor, field programmable gatearray (FPGA), memory circuitry, supporting power supplies, and so forth.In motor drive applications, the control circuitry 42 may be configuredto implement various desired control regimes, such as for speedregulation, torque control, vector control, start-up regimes, and soforth. In the embodiment illustrated in FIG. 1, various functionalcircuit boards 44 are linked to the control circuitry 42 and may beprovided for specific functions. For example, a wide range of optionsmay be implemented by the use of such circuitry, including the controlregimes mentioned above, as well as various communications options,safety options, and so forth.

The controller 22 will typically allow for connection to an operatorinterface, which may be local at the controller and/or remote from it.In a presently contemplated embodiment, for example, an operatorinterface 46 may be physically positioned on the controller 22 butremovable for hand-held interfacing. The interface circuitry (e.g.,portable computers) may also be coupled permanently or occasionally tothe controller 22, such as via Internet cabling, or other networkprotocols, including standard industrial control protocols. Finally, thecontroller 22 may be coupled to various remote monitoring and controlcircuitry as indicated by reference numeral 48. Such circuitry mayinclude monitoring stations, control stations, control rooms, remoteprogramming stations, and so forth. It should be noted that suchcircuitry may also include other drives, such that the operation of thesystem 10 may be coordinated, where desired, with that of otherequipment. Such coordination is particularly useful in automationsettings where a large number of operations are performed in acoordinated manner. Thus, the control circuitry 42 may form its controlin coordination with logic implemented by automation controllers,separate computers, and so forth.

FIG. 2 illustrates certain of the components that may be included withinthe individual drives described above. For example, the controlcircuitry 42 is illustrated as being coupled to power layer interfacecircuitry 50. Such circuitry will be provided in each drive and willoperate independently within the drive, but in a coordinated mannerunder the control of the control circuitry. The power layer interfacecircuitry may include a range of circuits, such as a dedicatedprocessor, memory, and so forth. In a presently contemplated embodiment,the power layer interface circuitry 50 includes an FPGA that implementsprogramming for carrying out control of the power electronic switcheswithin the individual drive. The power layer interface circuitry thuscommunicates with the power layer as indicated by reference numeral 52,which is itself comprised of sets of power electronic devices, such asIGBTs and diodes. These switches are illustrated generally by referencenumeral 54. In a typical arrangement, the switches may be provided on asingle support or on multiple supports. For example, in a presentlycontemplated embodiment separate supports are provided for each phase ofpower, with multiple IGBTs and diodes being provided on each support.These devices themselves may be constructed in any suitable manner, suchas direct bond copper stacks, lead frame packages, and so forth. Ingeneral, one or several types of feedback will be provided in thecircuitry as indicated by reference numeral 56. Such feedback mayinclude, for example, output voltages, output currents, temperatures,and so forth. Other feedback signals may be provided throughout thesystem, such as to allow the control circuitry to monitor the electricalparameters of the incoming power, the outgoing power, the DC bus power,and so forth.

FIG. 3 is a perspective view of an exemplary embodiment of a cabinet 58,within which components of a motor drive 60 are housed. As illustrated,the cabinet 58 includes an inverter 62 (e.g., including the invertercircuitry 36 of FIG. 1) and a converter 64 (e.g., including theconverter circuitry 28 of FIG. 1), among other components. The inverter62 is at least partially attached to an inverter duct 66, and theconverter 64 is at least partially attached to a converter duct 68. Morespecifically, the inverter 62 is sealingly attached to the inverter duct66 such that the inverter duct 66 supports the inverter 62 when theinverter duct 66 is removed from the cabinet 58, and the converter 64 issealingly attached to the converter duct 68 such that the converter duct68 supports the converter 64 when the converter duct 68 is removed fromthe cabinet 58. In addition, heat sink components of the inverter 62 andconverter 64 may be disposed within the inverter duct 66 and theconverter duct 68, respectively. In the illustrated embodiment, theinverter 62 and related components (e.g., the inverter duct 66) havebeen rolled out of the cabinet 58 and are separated from the converter64 and related components (e.g., the converter duct 68).

When coupled together, the inverter duct 66 and the converter duct 68form a duct system 70 or a portion of the duct system 70 for the motordrive 60. In addition, the inverter duct 66 is attached to an inlet airduct 72, within which a blower 74 is housed. The inlet air duct 72 mayalso be considered a component of the duct system 70. Indeed, in certainembodiments, the inverter duct 66 and the inlet air duct 72 may beintegrated into a single unit. However, in other embodiments, theinverter duct 66 and the inlet air duct 72 may be separate. As describedin greater detail below, the inverter duct 66, the converter duct 68,and an exhaust duct (not shown) may define a pair of parallel air flowchannels of the duct system 70, through which cooling air blown by theblower 74 may flow. As also described in greater detail below, theinverter duct 66, the converter duct 68, and the exhaust duct includeangled interfaces that mate during assembly of the inverter duct 66, theconverter duct 68, and the exhaust duct to form the duct system 70. Thecooling air flowing through the parallel air flow channel paths is usedto dissipate heat from the heat sinks associated with the inverter 62and the converter 64.

As illustrated by arrow 76 in FIG. 3, the inlet air duct 72 and theinverter duct 66 may be rolled into and out of the cabinet 58 when acabinet door 78 is opened. In particular, in certain embodiments, theinlet air duct 72 and the inverter duct 66 are integral with orpositioned on a transport device. In the illustrated embodiment, theinlet air duct 72 and the inverter duct 66 are placed on an auxiliarycart or platform 80 facilitate movement of the inlet air duct 72 andinverter duct 66 relative to the converter duct 68 and other aspects ofthe cabinet 58 such that field wiring of the motor drive 60 may beaccessed. The auxiliary cart or platform 80 illustrated in FIG. 3 is butone exemplary embodiment, and other types of auxiliary carts orplatforms 80 may be used to facilitate movement of the inlet air duct 72and inverter duct 66 relative to the converter duct 68 and other aspectsof the cabinet 58.

When considered together, the inverter 62, the inverter duct 66, theinlet air duct 72 (i.e., the inlet/inverter duct assembly 94), andassociated components are generally the heaviest portion of the motordrive 60. Accordingly, the ability of present embodiments to roll theinlet/inverter duct assembly 94 into and out of the cabinet 58facilitates maintenance of the motor drive 60 relative to traditionalsystems. In addition, in certain embodiments, the converter 64 andassociated converter duct 68 may be removed through the top of thecabinet 58 once an exhaust vent 88 is removed, as illustrated by arrow90. Indeed, some embodiments may include an integral hook or eyelet onthe converter duct 68 for this purpose. Locating the converter 64 andconverter duct 68 in the top portion of the cabinet 58 furtherfacilitates maintenance of the motor drive 60 because the converter 64and associated converter duct 68 are generally not as heavy as thecombined weight of the inlet/inverter duct assembly 94. In particular,the embodiments described herein increase the modularity of the motordrive 60 without including complicated joints and avoiding the need todisturb field wiring. For example, the inverter 62 and inverter duct 66may be removed without the need to remove the rest of the motor drive 60when the inverter 62 requires servicing. In particular, the inverterduct 66 may be capable of supporting the inverter 62 when the inverterduct 66 is removed from the cabinet 58 without removal of the inverter62 from the inverter duct 66. Similarly, the converter duct 68 may becapable of supporting the converter 64 when the converter duct 68 isremoved from the cabinet 58 without removal of the converter 64 from theconverter duct 68. Moreover, the inverter duct 66 and the converter duct68 may be capable of supporting the inverter 62 and the converter 64when the inverter duct 66 and the converter duct 68 are removed from thecabinet 58 together without removal of the inverter 62 from the inverterduct 66 and without removal of the converter 64 from the converter duct68.

When the system components are assembled, the cabinet door 78 is closed,and the motor drive 60 is in operation, air is drawn into the cabinet 58through vents 92 in the cabinet door 78, as illustrated by arrow 82. Theair drawn in through the vents 92 is then expelled through fans 84 inthe cabinet door 78 to discard waste heat in the cabinet 58, asillustrated by arrows 86. In addition, air 87 is also drawn into thecabinet 58 and into the inlet air duct 72, where it is blown by theblower 74 through parallel ducts channels of the inverter duct 66. Theair blown through the parallel duct channels of the inverter duct 66 isthen directed through the mated parallel duct channels of the converterduct 68. Then, the air directed through the parallel duct channels ofthe converter duct 68 is directed through mated parallel duct channelsof an exhaust duct and out of the top of the cabinet 58 through theexhaust vent 88. This air flow through the various duct segments passesover heat sinks associated with the inverter 62 and the converter 64 andprovides cooling for these components.

For example, FIG. 4 is a schematic diagram illustrating cooling air flowpaths through an exemplary embodiment of the duct system 70, whichincludes the inverter duct 66, the converter duct 68, and an exhaustduct 96. As illustrated, the inverter duct 66 is attached to at least aportion of the inverter 62, the converter duct 68 is attached to atleast a portion of the converter 64, and the exhaust duct 96 is attachedto no functional components of the motor drive 60. Inlet air flow 98 tothe duct system 70 is generated by the blower 74 and is initially splitinto a first air flow 100 and a second air flow 102 by separate channelsof the inverter duct 66. However, in other embodiments, the inlet airflow 98 may be split into separate flow paths prior to entering theinverter duct 66 (e.g., by a baffle or channels in the inlet air duct72). The first and second air flows 100, 102 proceed throughcorresponding channels of segments of the duct system 70 and encounterdifferent system components (e.g., heat sinks of the inverter 62 and theconverter 64), which cause different temperature changes in the air.Indeed, air coming into and out of a particular channel of a ductsegment will have different characteristics. Similarly, air exiting orentering a first channel of a duct segment will have characteristicsthat are different from air exiting or entering a second channel of thesame duct segment. Thus, while the air of each air flow 100, 102 remainsthe same, different portions of the air flow will have differenttemperatures, pressures, and velocities, and will be indicated by arrowswith different reference numbers based on location in the duct system 70to facilitate discussion.

As illustrated in FIG. 4, the first air flow 100 is blown into a firstinverter duct channel 104 of the inverter duct 66, and the second airflow 102 is blown into a second inverter duct channel 106 of theinverter duct 66. The second air flow 102 is used to dissipate heatgenerated by the inverter 62 through an inverter heat sink. Indeed, thesecond air flow 102 enters the second inverter duct channel 106, pullsheat away from the heat sink as it passes over the inverter 62, andexits the second inverter duct channel 106. This generally causes anincrease in the temperature of the air flow 102 and a reduction in thespeed of the air flow due to interaction with heat sink fins and soforth. In contrast, the first air flow 100 generally flows unimpededthrough the first inverter duct channel 104. Indeed, the first inverterduct channel 104 is substantially vacant and, thus, does notsubstantially obstruct the first air flow 100. In general, the firstinverter duct channel 104 and the second inverter duct channel 106 areadjacent to and parallel with each other and are partially defined byfront and back walls of the inverter duct 66 and an interior partitionwall, as described below. In other words, the first inverter ductchannel 104 and the second inverter duct channel 106 may share commonfront and back walls and the interior partition wall. However, incertain embodiments, the front wall locations of the first and/or secondinverter duct channels 104, 106 may be used to tune the air flow balancebetween the first and second inverter duct channels 104, 106.

Upon exiting the corresponding channels of the inverter duct 66, thefirst air flow 100 may be referred to as first air flow 108 and thesecond air flow 102 may be referred to as second air flow 110, asindicated by the corresponding arrows in FIG. 4. The first air flow 108exiting the first inverter duct 104 is directed into a first converterduct channel 112 of the converter duct 68, and the second air flow 110exiting the second inverter duct channel 106 is directed into a secondconverter duct channel 114 of the converter duct 68. Because the secondair flow 110 exiting the second inverter duct channel 106 was used tocarry away heat from the heat sink associated with the inverter 62, thetemperature of the second air flow 110 entering the second converterduct channel 114 will generally be higher than the temperature of thefirst air flow 108 entering the first converter duct channel 112. Thefirst air flow 108 in the first converter duct channel 112 is used todissipate heat generated by the converter 64 through a converter heatsink. Indeed, the first air flow 108 enters the first converter ductchannel 112, pulls heat away from the heat sink as it passes over theconverter 64, and exits the first converter duct channel 112. Thisgenerally causes an increase in the temperature of the first air flow108 and a reduction in the speed of the air flow due to interaction withheat sink fins and so forth. In contrast, the second air flow 110generally flows unimpeded through the second converter duct channel 114.Indeed, the second converter duct channel 114 is substantially vacantand, thus, does not substantially obstruct the second air flow 110. Ingeneral, the first converter duct channel 112 and the second converterduct channel 114 are adjacent to and parallel with each other and arepartially defined by front and back walls of the converter duct 68 andan interior partition wall, as described below. In other words, thefirst converter duct channel 112 and the second converter duct channel114 share common front and back walls and the interior partition wall.However, in certain embodiments, the front wall locations of the firstand/or second converter duct channels 112, 114 may be used to tune theair flow balance between the first and second converter duct channels112, 114.

Upon exiting the corresponding channels of the converter duct 68, thefirst air flow 108 may be referred to as first air flow 116 and thesecond air flow 110 may be referred to as second air flow 118, asindicated by the corresponding arrows in FIG. 4. The first air flow 116exiting the first converter duct channel 112 is directed into a firstexhaust duct channel 120 of the exhaust duct 96, and the second air flow118 exiting the second converter duct channel 114 is directed into asecond exhaust duct channel 122 of the exhaust duct 96. Because thefirst air flow 116 exiting the first converter duct channel 112 was usedto carry away heat from the heat sink associated with the converter 64,the temperature of the first air flow 116 exiting the first converterduct channel 112 will generally be higher than the temperature of thefirst air flow 108 entering the first converter duct channel 112. Thefirst and second air flows 116, 118 entering the first and secondexhaust duct channels 120, 122 generally flow unimpeded through thefirst and second exhaust duct channels 120, 122, respectively, and exitas first and second exhaust air flows 124, 126 through the exhaust vent88 in the top of the cabinet 58 of FIG. 3. In other words, both thefirst and second exhaust duct channels 120, 122 are substantiallyvacant. In general, the first exhaust duct channel 120 and the secondexhaust duct channel 122 are adjacent to and parallel with each otherand are partially defined by front and back walls of the exhaust duct 96and a common interior partition wall. In addition, in certainembodiments, the exhaust duct 96 may only include one common duct path,into which the first and second air flows 116, 118 may flow beforeexiting the exhaust duct 96.

The first inverter duct channel 104, first converter duct channel 112,and first exhaust duct channel 120 form a first duct channel path 128.Similarly, the second inverter duct channel 106, second converter ductchannel 114, and second exhaust duct channel 122 form a second ductchannel path 130. In general, the first air flow 100, 108, 116, 124through the first duct channel path 128 is used to dissipate and carryaway heat generated by the converter 64, whereas the second air flow102, 110, 118, 126 through the second duct channel path 130 is used todissipate and carry away heat generated by the inverter 62. The firstand second duct channel paths 128, 130 form parallel air cooling pathsthrough which the cooling air may be routed. In particular, the firstduct channel path 128 is dedicated to providing cooling air for the heatsink associated with the converter 64, and the second duct channel path130 is dedicated to providing cooling air for the heat sink associatedwith the inverter 62. As such, the parallel duct channel paths 128, 130eliminate preheating of the cooling air to downstream heat sinks, aswould occur if the duct channel paths 128, 130 were in series, becauseeach duct channel path 128, 130 receives ambient air. That is,essentially ambient air is passed over the respective heat sinks in eachduct channel path 128, 130 in accordance with the present embodimentsbecause the duct channel paths 128, 130 are in parallel instead of inseries.

In certain embodiments, the second duct channel path 130 may have asubstantially greater cross-sectional volume than the first duct channelpath 128, enabling higher cooling air flow rates across the heat sinkassociated with the inverter 62 than across the heat sink associatedwith the converter 64. In other words, the volumes of the parallel ductchannel paths 128, 130 are dimensioned to pass cooling air at volumes orrates configured to optimize the cooling of the inverter 62 and theconverter 64. This is due at least in part to the fact that the inverter62 typically generates more heat than the converter 64. The parallelduct channel paths 128, 130 allow for balancing of air flow through eachduct channel path 128, 130 inasmuch as the parallel duct channel paths128, 130 may be resized based on predicted heat generation of theinverter 62 and the converter 64. The parallel duct channel paths 128,130 also eliminate the need for individual blowers for each powersection, thereby reducing the size of the duct system 70 and the cabinet58 of FIG. 3. In certain embodiments, an inverter 62 may be used withouta converter 64 for common bus or parallel drive applications. In theseembodiments, the first duct channel path 128 may be blocked off at theinterface between the inverter duct 66 and the converter duct 68, and analternate duct section may be substituted for the converter duct 68.

As described above with respect to FIG. 3, the inverter duct 66 may berolled into and out of the cabinet 58 such that it is separated from theconverter duct 68, as illustrated by arrow 76 in FIG. 3. When theinverter duct 66 and the converter duct 68 are assembled together,mating angled surfaces of the inverter duct 66 and the converter duct 68abut each other, connecting the first inverter duct channel 104 with thefirst converter duct channel 112, and connecting the second inverterduct channel 106 with the second converter duct channel 114.

FIG. 5 is a perspective view of an exemplary embodiment of the converterduct 68 extracted from the cabinet 58 of FIG. 3. As illustrated, aconverter heat sink 132 having a plurality of heat sink fins 134extending into the first converter duct channel 112 is attached to theconverter duct 68. In addition, components 136 of the converter 64 areattached to the converter heat sink 132 on a side of the converter heatsink 132 opposite the plurality of heat sink fins 134 such that thecomponents 136 are external to the first converter duct channel 112. Asdescribed above, cooling air flowing through the first converter ductchannel 112 dissipates and carries away heat generated by the components136 of the converter 64. In particular, heat generated by the components136 of the converter 64 flows through the converter heat sink 132 andassociated heat sink fins 134 into the first converter duct channel 112.The heat is then transferred from the heat sink fins 134 to cooling airflowing from an upstream end 138 of the converter duct 68 and carried toa downstream end 140 of the converter duct 68 through the firstconverter duct channel 112.

As illustrated, the converter duct 68 includes an angled upstream end138 that mates with a downstream end of the inverter duct 66 asdescribed below. In particular, in certain embodiments, the upstream end138 of the converter duct 68 extends out from a front wall 142 of theconverter duct 68 to a back wall 144 of the converter duct 68 at anoblique angle (i.e., not a right angle). More specifically, the upstreamend 138 of the converter duct 68 is at an obtuse angle (e.g., greaterthan 90° angle) with respect to the front wall 142 of the converter duct68, and is at an acute angle (e.g., less than 90° angle) with respect tothe back wall 144 of the converter duct 68. For example, in certainembodiments, the angle of the upstream end 138 with respect to the frontwall 142 of the converter duct 68 is approximately 135° (see, e.g.,angle θ illustrated in FIG. 8), whereas the angle of the upstream end138 with respect to the back wall 144 of the converter duct 68 isapproximately 45° (see, e.g., angle φ illustrated in FIG. 8). The 45°and 135° angles optimize the sealing of both the front wall 142 and theback wall 144 with the upstream end 138 of the converter duct 68.

The first converter duct channel 112 of the converter duct 68 is definedbetween the front and back walls 142, 144 of the converter duct 68, aleft wall 146 of the converter duct 68, and an interior partition wall148 extending from the front wall 142 to the back wall 144 within theconverter duct 68. The second converter duct channel 114 of theconverter duct 68 is defined between the front and back walls 142, 144of the converter duct 68, a right wall 150 of the converter duct 68, andthe interior partition wall 148 extending from the front wall 142 to theback wall 144 within the converter duct 68.

The converter duct 68 includes generally rectangular-shaped or obroundkeys 152 attached to both the left and right walls 146, 150 of theconverter duct 68. In particular, in certain embodiments, the keys 152are attached to the left and right walls 146, 150 of the converter duct68 via two or more fasteners 154. As described in greater detail below,the keys 152 are configured to mate with brackets attached to theinverter duct 66 to align the converter duct 68 with the inverter duct66 when the converter duct 68 and the inverter duct 66 are assembledtogether. In addition, the keys 152 include keyholes 156 extending atleast partially through the keys 152 from front to back. As alsodescribed in greater detail below, the keyholes 156 are configured tomate with pins that help secure the converter duct 68 to the inverterduct 66 when the converter duct 68 and the inverter duct 66 areassembled together. The converter duct 68 also includes at least oneadditional alignment feature 158 extending from the left and right walls146, 150 of the converter duct 68. The alignment features 158 are alsoconfigured to mate with the brackets attached to the inverter duct 66 toalign the converter duct 68 with the inverter duct 66 when the converterduct 68 and the inverter duct 66 are assembled together. In addition, incertain embodiments, the alignment features 158 may act as additionalkeys.

FIG. 6 is a perspective view of an exemplary embodiment of the inverterduct 66 extracted from the cabinet 58 of FIG. 3. As illustrated, aninverter heat sink 160 having a plurality of heat sink fins 162extending into the second inverter duct channel 106 is attached to theinverter duct 66. In addition, components 164 of the inverter 62 areattached to the inverter heat sink 160 on a side of the inverter heatsink 160 opposite the plurality of heat sink fins 162 such that thecomponents 164 are external to the second inverter duct channel 106. Asdescribed above, cooling air flowing through the second inverter ductchannel 106 dissipates and carries away heat generated by the components164 of the inverter 62. In particular, heat generated by the components164 of the inverter 62 flow through the inverter heat sink 160 andassociated heat sink fins 162 into the second inverter duct channel 106.The heat is then transferred from the heat sink fins 162 to cooling airflowing from an upstream end 166 of the inverter duct 66 and carried toa downstream end 168 of the inverter duct 66 through the second inverterduct channel 106.

As illustrated, the inverter duct 66 includes an angled downstream end168 that mates with the angled upstream end 138 of the converter duct 68described above. In particular, in certain embodiments, the downstreamend 168 of the inverter duct 66 extends out from a back wall 170 of theinverter duct 66 to a front wall 172 of the inverter duct 66 at anoblique angle (i.e., not a right angle). More specifically, thedownstream end 168 of the inverter duct 66 is at an obtuse angle (e.g.,greater than 90° angle) with respect to the back wall 170 of theinverter duct 66, and is at an acute angle (e.g., less than 90° angle)with respect to the front wall 172 of the inverter duct 66. For example,in certain embodiments, the angle of the downstream end 168 with respectto the back wall 170 of the inverter duct 66 is approximately 135°,whereas the angle of the downstream end 168 with respect to the frontwall 172 of the inverter duct 66 is approximately 45°. The 45° and 135°angles (or, indeed, any suitable supplementary angles) optimize thesealing of both the back wall 170 and the front wall 172 with thedownstream end 168 of the inverter duct 66.

The second inverter duct channel 106 of the inverter duct 66 is definedbetween the front and back walls 172, 170 of the inverter duct 66, aright wall 174 of the inverter duct 66, and an interior partition wall176 extending from the front wall 172 to the back wall 170 within theinverter duct 66. The first inverter duct channel 104 of the inverterduct 66 is defined between the front and back walls 172, 170 of theinverter duct 66, a left wall 178 of the inverter duct 66, and theinterior partition wall 176 extending from the front wall 172 to theback wall 170 within the inverter duct 66.

The inverter duct 66 includes brackets 180 attached to both the rightand left walls 174, 178 of the inverter duct 66. The brackets 180constrain motion in orthogonal directions to ensure proper ductalignment and seal compression. In particular, the brackets 180 areconfigured to draw the inverter duct 66 and the converter duct 68 intosealed engagement via a set of fasteners. The brackets 180 areintegrated structural components of the duct system 70 and provide apath for load transfer during lifting or raising from horizontal tovertical orientations. In addition, the brackets 180 also includelifting holes to lift the inverter duct 66 when the inverter duct 66 isdecoupled from the converter duct 68. Besides joining the inverter andconverter ducts 66, 68 together, the brackets 180 also provide a meansto secure the motor drive to the cabinet 58 of FIG. 3, as well asproviding a path for load transfer when lifting the entire motor drive.

As described in greater detail below, the brackets 180 are configured tomate with the keys 152 and alignment features 158 of the converter duct68 described above with respect to FIG. 5. In particular, the brackets180 include generally open-ended rectangular-shaped or obround slots 182configured to mate with the generally rectangular-shaped keys 152 of theconverter duct 68 to align the inverter duct 66 with the converter duct68 when the inverter duct 66 and the converter duct 68 are assembledtogether. In addition, the brackets 180 include at least one alignmentslot 184 configured to mate with the alignment features 158 of theconverter duct 68 to align the inverter duct 66 with the converter duct68 when the inverter duct 66 and the converter duct 68 are assembledtogether.

Each of the brackets 180 may be associated with a respective pin 186. Inparticular, the pins 186 may be configured to mate with the keyholes 156extending at least partially through the keys 152 of the converter duct68. When the inverter duct 66 and the converter duct 68 are assembledtogether, the pins 186 may be attached to the keys 152 of the converterduct 68, thereby securing the inverter duct 66 to the converter duct 68.Any suitable attachment features may be used for the keyholes 156 of thekeys 152 of the converter duct 68 and the pins 186 of the brackets 180of the inverter duct 66. For example, in certain embodiments, thekeyholes 156 and the pins 186 may be threaded such that the pins 186 arescrewed into the keyholes 156. It should be noted that, in certainembodiments, the inverter duct 66 may include the keys and alignmentfeatures, and the converter duct 68 may include the brackets, slots, andpins. In other words, the attachment features of the inverter duct 66and the converter duct 68 may be reversed from the embodimentsillustrated in FIGS. 5 and 6.

In addition, in certain embodiments, a gasket-like seal 188 may beattached to the downstream end 168 of the inverter duct 66 such that theseal 188 is compressed between and separates the inverter duct 66 fromthe converter duct 68 when the inverter duct 66 and the converter duct68 are assembled together. The seal 188 provides sealing capabilitiesthat maintain the air flow through the first and second duct channelpaths 128, 130 described above with respect to FIG. 4 with little to noleakage. In addition, the seal 188 prevents ingress of debris into thecabinet 58 of FIG. 3 from the first and second duct channel paths 128,130, thereby protecting sensitive components in the cabinet 58. Inparticular, the seal 188 forms a NEMA 12/IP54 seal without the use ofadhesive sealants, while also eliminating the need for restrictiveintake filters. The seal 188 also includes gasket stops to prevent overcompression and to transfer some of the loads between the inverter duct66 and the converter duct 68. In particular, in certain embodiments, theseal 188 is comprised of a generally compressible material, such as foamor the like.

FIGS. 7 and 8 are perspective and side exploded views of an exemplaryembodiment of the inverter duct 66, converter duct 68, inlet air duct72, and exhaust duct 96. As illustrated by arrow 76, the inverter duct66 and the inlet air duct 72 may be separated from the converter duct68. In particular, as described above, the inverter duct 66 and theinlet air duct 72 may be rolled into and out of the cabinet 58 describedabove with respect to FIG. 3. To facilitate the rolling, the inlet airduct 72 may include wheels 190 that may be rolled onto an auxiliary cartor platform 80 with respect to FIG. 3. When the inverter duct 66 isrolled out of the cabinet 58, the brackets 180 of the inverter duct 66are detached from the keys 152 and the alignment features 158 of theconverter duct 68. Conversely, when the inverter duct 66 is rolled backinto the cabinet 58, the brackets 180 of the inverter duct 66 areattached to the keys 152 and the alignment features 158 of the converterduct 68, providing both alignment and structural support of the inverterduct 66 with respect to the converter duct 68. Thus, by simply slidingthe inverter duct 66 into the cabinet 58 and engaging the inverter duct66 with the converter duct 68, the components function together to alignand seal the first and second duct channel paths 128, 130.

In addition, as described in greater detail below, the exhaust duct 96and the converter duct 68 may include similar attachment features asthose between the inverter duct 66 and the converter duct 68. Asillustrated by arrows 192 and 194, the exhaust duct 96 may be detachedfrom the converter duct 68 and lifted through the top of the cabinet 58of FIG. 3. In addition, once the exhaust duct 96 has been removed, theconverter duct 68 may also be lifted through the top of the cabinet 58of FIG. 3, as illustrated by arrow 90. In particular, in certainembodiments, the converter duct 68 may include a lifting bar 196 on thefront wall 142 of the converter duct 68 near the downstream end 140 ofthe converter duct 68, which facilitates lifting of the converter duct68 and attached ducts and/or components. When assembling the motor drive60, the converter duct 68 may first be inserted back into the cabinet 58of FIG. 3, as illustrated by arrow 90, and attached within the cabinet58. Once the converter duct 68 has been inserted and attached, theexhaust duct 96 may be inserted back into the cabinet 58 of FIG. 3 andattached to the converter duct 68, as illustrated by arrow 194 and 192.However, in other embodiments, the converter duct 68 may be rolled intoand out of the cabinet 58 of FIG. 3 while attached to the inverter duct66 and the inlet air duct 72, and the exhaust duct 96 may remain in thecabinet 58.

As described above, the inverter duct 66 and the converter duct 68 areattachable and detachable from each other at the downstream end 168 ofthe inverter duct 66 and the upstream end 138 of the converter duct 68.FIG. 9 is a partial perspective view of an exemplary embodiment of theinverter duct 66 and the converter duct 68 when detached from eachother, and FIG. 10 is a partial perspective view of an exemplaryembodiment of the inverter duct 66 and the converter duct 68 whenattached to each other. As illustrated by arrow 76, the inverter duct 66and the converter duct 68 may be attached and detached by aligning thegenerally rectangular-shaped keys 152 of the converter duct 68 with thegenerally rectangular-shaped slots 182 of the brackets 180 of theinverter duct 66, aligning the alignment features 158 of the converterduct 68 with the alignment slots 184 of the brackets 180 of the inverterduct 66, and inserting and attaching the pins 186 of the inverter duct66 within the keyholes 156 of the keys 152 of the converter duct 68. Inparticular, the obround shape of the keys 152 facilitates the alignmentof the inverter duct 66 with the converter duct 68. More specifically,because of the slightly rounded edges of the keys 152, slight variationsin the alignment will be corrected relatively smoothly than if sharpedges were used. In addition, in other embodiments, trapezoidal-shapedkeys 152 may be used with trapezoidal-shaped alignment slots 182.Although the majority of the brackets 180 are parallel with the rightand left walls 174, 178 of the inverter duct 66, the brackets 180 mayalso include relatively narrow sections 198 that extend away from theinverter duct 66 orthogonal from the right and left walls 174, 178 ofthe inverter duct 66, wherein the narrow sections 198 are used to securethe inverter and converter ducts 66, 68 to the cabinet 58 of FIG. 3. Thepins 186 may be inserted into holes 200 in the narrow bracket sections198 before being inserted into and attached to the keyholes 156 of thekeys 152 of the converter duct 68. Although described herein as beingused in motor drive systems, the disclosed techniques for attaching airduct systems may be extended to other applications, such as heating,ventilation, and air conditioning (HVAC) applications.

As described above with respect to FIGS. 7 and 8, the exhaust duct 96may also be detached from and attached to the converter duct 68. Indeed,in certain embodiments, the exhaust duct 96 and the converter duct 68may also include attachment features similar to those used to attach theconverter duct 68 and the inverter duct 66. FIG. 11 is a partialperspective view of an exemplary embodiment of the exhaust duct 96, theconverter duct 68, and the inverter duct 66. As illustrated, the exhaustduct 96 includes an angled upstream end 202 that mates with a downstreamend 204 of the converter duct 68. In particular, in certain embodiments,the upstream end 202 of the exhaust duct 96 extends out from a frontwall 206 of the exhaust duct 96 to a back wall 208 of the exhaust duct96 at an oblique angle (i.e., not a right angle). More specifically, theupstream end 202 of the exhaust duct 96 is at an obtuse angle (e.g.,greater than 90° angle) with respect to the front wall 206 of theexhaust duct 96, and is at an acute angle (e.g., less than 90° angle)with respect to the back wall 208 of the exhaust duct 96. For example,in certain embodiments, the angle of the upstream end 202 with respectto the front wall 206 of the exhaust duct 96 is approximately 135°,whereas the angle of the upstream end 202 with respect to the back wall208 of the exhaust duct 96 is approximately 45°. The 45° and 135° anglesoptimize the sealing of both the front wall 206 and the back wall 208with the upstream end 202 of the exhaust duct 96.

The exhaust duct 96 includes generally rectangular-shaped or obroundkeys 210 attached to both left and right walls 212, 214 of the exhaustduct 96. In particular, in certain embodiments, the keys 210 areattached to the left and right walls 212, 214 of the exhaust duct 96 viatwo or more cap screws 216. The keys 210 are configured to mate withbrackets 218 attached to the converter duct 68 to align the exhaust duct96 with the converter duct 68 when the exhaust duct 96 and the converterduct 68 are assembled together. In addition, the keys 210 includekeyholes 220 extending at least partially through the keys 210 fromfront to back. The keyholes 220 are configured to mate with pins 222that help secure the exhaust duct 96 to the converter duct 68 when theexhaust duct 96 and the converter duct 68 are assembled together.Although not illustrated in the embodiment of FIG. 11, in certainembodiments, the exhaust duct 96 may also include at least oneadditional alignment feature extending from the left and right walls212, 214 of the exhaust duct 96. The alignment features may also beconfigured to mate with the brackets 218 attached to the converter duct68 to align the exhaust duct 96 with the converter duct 68 when theexhaust duct 96 and the converter duct 68 are assembled together.

As illustrated, the converter duct 68 includes an angled downstream end204 that mates with the angled upstream end 202 of the exhaust duct 96described above. In particular, in certain embodiments, the downstreamend 204 of the converter duct 68 extends out from the back wall 144 ofthe converter duct 68 to the front wall 142 of the converter duct 68 atan oblique angle (i.e., not a right angle). More specifically, thedownstream end 204 of the converter duct 68 is at an obtuse angle (e.g.,greater than 90° angle) with respect to the back wall 144 of theconverter duct 68, and is at an acute angle (e.g., less than 90° angle)with respect to the front wall 142 of the converter duct 68. Forexample, in certain embodiments, the angle of the downstream end 204with respect to the back wall 144 of the converter duct 68 isapproximately 135°, whereas the angle of the downstream end 204 withrespect to the front wall 142 of the converter duct 68 is approximately45°. The 45° and 135° angles (or, indeed, any suitable supplementaryangles) optimize the sealing of both the front wall 142 and the backwall 144 with the downstream end 204 of the converter duct 68.

The converter duct 68 includes a bracket 218 attached to both the leftand right walls 146, 150 of the converter duct 68. The brackets 218constrain motion in orthogonal directions to ensure proper ductalignment and seal compression. In particular, the brackets 218 areconfigured to draw the exhaust duct 96 and the converter duct 68 intosealed engagement via a set of fasteners. The brackets 218 areintegrated structural components of the duct system 70 and provide apath for load transfer during lifting of the motor drive 60. Thebrackets 218 are configured to mate with the keys 210 of the exhaustduct 96 described above. In particular, the brackets 218 includegenerally open-ended rectangular-shaped or obround slots 224 configuredto mate with the generally rectangular-shaped keys 210 of the exhaustduct 96 to align the converter duct 68 with the exhaust duct 96 when theconverter duct 68 and the exhaust duct 96 are assembled together.However, as described above, other shapes may be used for the keys 210and the slots 224. In addition, although not illustrated in theembodiment of FIG. 11, the brackets 218 may also include alignment slotsconfigured to mate with alignment features of the exhaust duct 96 toalign the converter duct 68 with the exhaust duct 96 when the converterduct 68 and the exhaust duct 96 are assembled together.

Each of the brackets 218 may be associated with a respective pin 222. Inparticular, the pins 222 may be configured to mate with the keyholes 220extending at least partially through the keys 210 of the exhaust duct96. When the converter duct 68 and the exhaust duct 96 are assembledtogether, the pins 222 may be attached to the keys 210 of the exhaustduct 96, thereby securing the converter duct 68 to the exhaust duct 96.Any suitable attachment features may be used for the keyholes 220 of thekeys 210 of the exhaust duct 96 and the pins 222 of the brackets 218 ofthe converter duct 68. For example, in certain embodiments, the keyholes220 and the pins 222 may be threaded such that the pins 222 are screwedinto the keyholes 220.

In addition, in certain embodiments, a gasket-like seal 226 may beattached to the downstream end 204 of the converter duct 68 such thatthe seal 226 separates the converter duct 68 from the exhaust duct 96when the converter duct 68 and the exhaust duct 96 are assembledtogether. The seal 226 provides sealing capabilities that maintains theair flow through the first and second duct channel paths 128, 130described above with respect to FIG. 4 with little to no leakage. Inaddition, the seal 226 prevents ingress of debris into the cabinet 58 ofFIG. 3 from the first and second duct channel paths 128, 130, therebyprotecting sensitive components in the cabinet 58. In particular, theseal 226 forms a NEMA 12/IP54 seal without the use of adhesive sealants,while also eliminating the need for restrictive intake filters. The seal226 also includes gasket stops to prevent over compression and totransfer some of the loads between the converter duct 68 and the exhaustduct 96. In particular, in certain embodiments, the seal 226 iscomprised of a generally compressible material, such as foam or thelike.

As illustrated by arrow 192, the exhaust duct 96 and the converter duct68 may be attached and detached by aligning the generallyrectangular-shaped keys 210 of the exhaust duct 96 with the generallyrectangular-shaped slots 224 of the brackets 218 of the converter duct68, and inserting and attaching the pins 222 of the converter duct 68within the keyholes 220 of the keys 210 of the exhaust duct 96. Asdescribed above, other shapes may be used for the keys 210 and the slots224. Although the majority of the brackets 218 are parallel with theleft and right walls 146, 150 of the converter duct 68, the brackets 218also include relatively narrow sections 228 that extend away from theconverter duct 68 orthogonal from the left and right walls 146, 150 ofthe converter duct 68, wherein the narrow sections 228 are used tosecure the converter and exhaust ducts 68, 96 to the cabinet 58 of FIG.3. The pins 222 are inserted into holes 230 in the narrow bracketsections 228 before being inserted into and attached to the keyholes 220of the keys 210 of the exhaust duct 96.

As described above with respect to FIGS. 4 through 6, the first ductchannel path 128 is dedicated to cooling the converter heat sink 132associated with the converter 64, whereas the second duct channel path130 is dedicated to cooling the inverter heat sink 160 associated withthe inverter 62. In particular, the first converter duct channel 112 ofthe converter duct 68 houses the converter heat sink 132, and the secondinverter duct channel 106 of the inverter duct 66 houses the inverterheat sink 160. More specifically, the heat sink fins 134 of theconverter heat sink 132 are disposed within the first converter ductchannel 112 of the converter duct 68, and the heat sink fins 162 of theinverter heat sink 160 are disposed within the second inverter ductchannel 106.

FIG. 12 is a front view of an exemplary embodiment of the inverter duct66, and FIG. 13 is a cross-sectional side view of an exemplaryembodiment of the second inverter duct channel 106 of the inverter duct66. As illustrated, the second inverter duct channel 106 of the inverterduct 66 includes a baffled wall 232 near the back wall 170 of theinverter duct 66. In addition to providing structural strength to theinverter duct 66, the baffled wall 232 includes multiple sectionsconfigured to gradually reduce the cross-sectional area of the secondinverter duct channel 106 as the cooling air 102, 110 flows from theupstream end 166 of the inverter duct 66 to the downstream end 168 ofthe inverter duct 66. In particular, the cross-section of theillustrated baffled wall 232 includes first, second, and third baffledwall sections 234, 236, 238 separated by first and second baffles 240,242 such that the first, second, and third baffled wall sections 234,236, 238 generally correspond to the three components 164 (e.g.,switching modules) of the inverter 62. However, in other embodiments,any number of baffled wall sections may be used for the baffled wall232. For example, the baffled wall 232 may include 2, 3, 4, 5, 6, 7, 8,9, 10, or even more baffled wall sections.

As illustrated, both of the baffles 240, 242 may transition at an angleof approximately 45° from one baffled wall section to the next. Forexample, the first baffle 240 may transition at an angle ofapproximately 45° from the first baffled wall section 234 to the secondbaffled wall section 236, and the second baffle 242 may transition at anangle of approximately 45° from the second baffled wall section 236 tothe third baffled wall section 238. However, it should be noted that thefirst and second baffles 240, 242 may transition between baffled wallsections at other angles in other embodiments. Because of the first andsecond baffles 240, 242, a distance 244 from a base 246 of the inverterheat sink 160 to the first baffled wall section 234 is slightly greaterthan a distance 248 from the base 246 of the inverter heat sink 160 tothe second baffled wall section 236 which is, in turn, slightly greaterthan a distance 250 from the base 246 of the inverter heat sink 160 tothe third baffled wall section 238.

Because of the gradual decrease in the distance from the base 246 of theinverter heat sink 160 to the baffled wall 232, the cross-sectional areaof the second inverter duct channel 106 through which the cooling air102, 110 flows is gradually reduced. As such, the velocity of thecooling air 110 near the downstream end 168 of the second inverter ductchannel 106 will be greater than the velocity of the cooling air 102near the upstream end 166 of the second inverter duct channel 106. Inparticular, a portion of the cooling air bypasses the heat sink fins 162near the first baffled wall section 234 and flows across the heat sinkfins 162 near the second and third baffled wall sections 236, 238,whereas another portion of the cooling air bypasses the heat sink fins162 near the second baffled wall section 236 and flows across the heatsink fins 162 near the third baffled wall section 238. In other words, aportion of the cooling air flows directly through or between the heatsink fins 162, whereas some of the cooling air flows in the area betweenthe heat sink fins 162 and the baffled wall 232. As the area between theheat sink fins 162 and the baffled wall 232 narrows because of thebaffles 240, 242, some of the cooling air that was initially flowingnear the baffled wall 232 will flow through the heat sink fins 162 atdownstream locations. The baffles 240, 242 provide relatively smoothtransitions in the air flow to reduce backpressure.

As a result of employing the baffled wall sections 234, 236, 238 asdiscussed above, the bypass air (which is at ambient temperature) isreintroduced at downstream locations to help reduce the temperaturegradients from the upstream components 164 of the inverter 62 to thedownstream components 164 of the inverter 62. More specifically, thebaffled wall 232 may enable the temperature gradient to be maintainedwithin 5° F. (e.g., from the upstream end 166 of the second inverterduct channel 106 to the downstream end 168 of the second inverter ductchannel 106) depending on heat load and positioning of the components164. Because of heat transfer from the heat sink fins 162, the coolingair 102, 110 may gradually increase in temperature as it flows throughthe second inverter duct channel 106. However, this increase intemperature may be at least partially offset because more cooling air102, 110 is directed to flow directly between the heat sink fins 162 atdownstream locations.

The first converter duct channel 112 of the converter duct 68 alsoincludes a baffled wall similar to the baffled wall 232 in the secondinverter duct channel 106 of the inverter duct 66. FIG. 14 is a frontview of an exemplary embodiment of the converter duct 68, and FIG. 15 isa cross-sectional side view of an exemplary embodiment of the firstconverter duct channel 112 of the converter duct 68. As illustrated, thefirst converter duct channel 112 of the converter duct 68 includes abaffled wall 252 near the back wall 144 of the converter duct 68. Inaddition to providing structural strength to the converter duct 68, thebaffled wall 252 includes multiple sections configured to graduallyreduce the cross-sectional area of the first converter duct channel 112as the cooling air 108, 116 flows from the upstream end 138 of theconverter duct 68 to the downstream end 140 of the converter duct 68. Inparticular, the cross-section of the illustrated baffled wall 252includes first and second baffled wall sections 254, 256 separated by abaffle 258. However, in other embodiments, any number of baffled wallsections may be used for the baffled wall 252. For example, the baffledwall 252 may include 2, 3, 4, 5, 6, 7, 8, 9, 10, or even more baffledwall sections.

As illustrated, the baffle 258 may transition at an angle ofapproximately 45° from the first baffled wall section 254 to the secondbaffled wall section 256. However, it should be noted that the baffle258 may transition from the first baffled wall section 254 to the secondbaffled wall section 256 at other angles in other embodiments. Becauseof the baffle 258, a distance 260 from a base 262 of the converter heatsink 132 to the first baffled wall section 254 is slightly greater thana distance 264 from the base 262 of the converter heat sink 132 to thesecond baffled wall section 256. Because of the gradual decrease in thedistance from the base 262 of the converter heat sink 132 to the baffledwall 252, the cross-sectional area of the first converter duct channel112 through which the cooling air 108, 116 flows is gradually reduced.As such, the velocity of the cooling air 116 near the downstream end 140of the first converter duct channel 112 will be greater than thevelocity of the cooling air 108 near the upstream end 138 of the firstconverter duct channel 112. In particular, a portion of the cooling airbypasses the heat sink fins 134 near the first baffled wall section 254and flows across the heat sink fins 134 near the second baffled wallsection 256. In other words, a portion of the cooling air flows directlythrough the heat sink fins 134, whereas some of the cooling air flows inthe area between the heat sink fins 134 and the baffled wall 252. Someof the cooling air flowing near the baffled wall 252 will flow throughthe heat sink fins 134 at downstream locations because of the baffle258. The baffle 258 provides relatively smooth transitions in the airflow to reduce backpressure. In addition, in certain embodiments, theheat sink fins 134 of the converter heat sink 132 may extend into theexhaust duct 96 to maintain air flow through the heat sink fins 134 andto provide a smooth transition into the exhaust duct 96.

As a result of employing the baffled wall sections 254, 256 as discussedabove, the bypass air (which is at ambient temperature) is reintroducedat downstream locations to help reduce the temperature gradients fromthe upstream components 136 of the converter 64 to the downstreamcomponents 136 of the converter 64. More specifically, the baffled wall252 may enable the temperature gradient to be maintained within 5° F.(e.g., from the upstream end 138 of the first converter duct channel 112to the downstream end 140 of the first converter duct channel 112)depending on heat load and positioning of the components 136. Because ofheat transfer from the heat sink fins 134, the cooling air 108, 116 maygradually increase in temperature as it flows through the firstconverter duct channel 112. However, this increase in temperature may beat least partially offset because more cooling air 108, 116 is directedacross the heat sink fins 134 at downstream locations.

FIG. 16 is a conceptual side view of an exemplary embodiment of theinverter heat sink 160 and the baffled wall 232 of the inverter duct 66of FIG. 13, illustrating how the cooling air flows are directed acrossthe heat sink fins 162 by the baffled wall 232. It should be noted thatthe relative dimensions illustrated in FIG. 16 are somewhat exaggeratedin order to illustrate how the cooling air flows are affected by thebaffled wall 232. As illustrated, a heat sink portion 266 of the coolingair 102 flowing into the second inverter duct channel 106 may directlyflow across and between the heat sink fins 162 of the inverter heat sink160, whereas a baffle portion 268 of the cooling air 102 flowing intothe second inverter duct channel 106 may bypass the heat sink fins 162of the inverter heat sink 160 through a distance 270 between the heatsink fins 162 and the first baffled wall section 234. A first portion272 of the baffle portion 268 of cooling air may introduce ambient airjust upstream of the second (e.g., middle) component 164 of the inverter62, and may rejoin the heat sink portion 266 flowing across and betweenthe heat sink fins 162 near where the heat sink fins 162 align with thefirst baffle 240 whereas some of the baffle portion 268 of cooling airmay continue to bypass the heat sink fins 162 through a distance 274between the heat sink fins 162 and the second baffled wall section 236.In addition, a second portion 276 of the baffle portion 268 of coolingair may introduce ambient air just upstream of the third (e.g.,downstream) component 164 of the inverter 62, and may rejoin the heatsink portion 266 flowing across and between the heat sink fins 162 nearwhere the heat sink fins 162 align with the second baffle 242, whereassome of the baffle portion 268 of cooling air may continue to bypass theheat sink fins 162 through a distance 278 between the heat sink fins 162and the third baffled wall section 238. The distance 278 between theheat sink fins 162 and the third baffled wall section 238 may also bedesigned to adjust the backpressure (e.g., balance the air flow betweenthe air flow channels). Finally, the remainder of the baffle portion 268may exit the second inverter duct channel 106. As such, more cooling airis directed across the heat sink fins 162 of the inverter heat sink 160toward the downstream end 168 of the second inverter duct channel 106than toward the upstream end 166 of the second inverter duct channel106. The same type of distribution of cooling air will occur withrespect to the heat sink fins 134 of the converter heat sink 132 and thebaffled wall 252 illustrated in FIG. 15.

As described above, the inverter duct 66 may be attached to an inlet airduct 72 that receives ambient air and blows the air through the parallelduct channel paths 128, 130 of FIG. 4. FIGS. 17 and 18 are a partialperspective view and a partial cross-sectional side view of an exemplaryembodiment of the inverter duct 66 and the inlet air duct 72. Asillustrated by arrow 280, inlet air may be received (e.g., through thevents 92 of the cabinet 58 illustrated in FIG. 3) through an aperture282 in the inlet air duct 72. In certain embodiments, a DC line chokemay be held in place within the aperture 282, and may be cooled by theinlet air 280. In addition, inlet air 87 may be received into aninterior volume 284 of the inlet air duct 72 through a vent in thecabinet door 78 of FIG. 3 directly in front of the blower 74. The inletair 87 from the interior volume 284 may be blown by the blower 74through the first inverter duct channel 104 and the second inverter ductchannel 106 of the inverter duct 66, respectively, as the first air flow100 and the second air flow 102 described above. In addition, in certainembodiments, a guide vane 286 may be attached to a base 288 of theinterior partition wall 176 of the inverter duct 66. The guide vane 286will control the flow of cooling air through the first and second ductchannel paths 128, 130. More specifically, the guide vane 286 willbalance the flow of the inlet air 87 blown by the blower 74 between thefirst and second air flows 100, 102. In particular, in certainembodiments, the guide vane 286 may be rotated about the base 288 of theinterior partition wall 176 to selectively adjust the amount of coolingair divided between the first and second duct channel paths 128, 130.The rotational positioning of the guide vane 286 may be adjustedmanually or automatically prior to or during operation of the motordrive 60. For example, the guide vane 286 may tune the flow of coolingair such that more cooling air is directed through the second ductchannel path 130 and over the inverter heat sink 160 than through thefirst duct channel path 128 and over the converter heat sink 132. Inaddition, the guide vane 286 reduces turbulence caused by vortexshedding that would otherwise occur at the base 288 of the interiorpartition wall 176. Reducing turbulence reduces backpressure andincreases air flow. In addition, the use of the guide vane 286 allowsfor a single blower 74 with a common air source (e.g., the inlet air 87)to be used to supply cooling air to the first and second duct channelpaths 128, 130.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A ducted electrical power conversion system, comprising: a first structural duct assembly configured to sealingly receive a converter; the converter supported on the first structural duct assembly, a converter heat sink of the converter extending into a converter cooling air channel of the first structural duct assembly; a second structural duct assembly mated to the first structural duct assembly and configured to sealingly receive an inverter; and the inverter supported on the second structural duct assembly, an inverter heat sink of the inverter extending into an inverter cooling air channel of the second structural duct assembly.
 2. The system of claim 1, wherein each of the first and second structural duct assemblies includes a respective partition separating the converter and inverter cooling air channels into separate first and second air channels.
 3. The system of claim 2, wherein the first air channel defined by the respective partition directs cooling air past the inverter, without cooling the inverter, into contact with the converter heat sink.
 4. The system of claim 3, wherein the second air channel defined by the respective partition directs cooling air into contact with the inverter heat sink and past the converter, without cooling the converter.
 5. The system of claim 2, comprising a guide vane adjacent to a base of one of the partitions for controlling flow of cooling air through the first and second air channels.
 6. The system of claim 5, wherein the guide vane is disposed adjacent to an inlet air duct in which a blower directs air into the first and second structural duct assemblies.
 7. The system of claim 1, wherein the first structural duct assembly comprises at least one wall section having a step or baffle configured to direct cooling air into contact with the converter heat sink.
 8. The system of claim 1, wherein the second structural duct assembly comprises at least one wall section having a step or baffle configured to direct cooling air into contact with the inverter heat sink.
 9. The system of claim 8, wherein the inverter comprises three or more separate switching modules for converting DC power to controlled frequency AC power, and wherein the second structural duct assembly comprises at least one wall section having a plurality of steps or baffles configured to direct cooling air towards a portion of the inverter heat sink generally corresponding to locations of the three or more separate switching modules.
 10. The system of claim 1, wherein the first structural duct assembly is capable of supporting the converter when the first structural duct assembly is lifted for displacement without removal of the converter from the first structural duct assembly.
 11. The system of claim 1, wherein the second structural duct assembly is capable of supporting the inverter when the second structural duct assembly is lifted for displacement without removal of the inverter from the second structural duct assembly.
 12. The system of claim 1, wherein the first and second structural duct assemblies are capable of supporting the inverter and the converter when the first and second structural duct assemblies are lifted together for displacement without removal of the converter from the first structural duct assembly and without removal of the inverter from the second structural duct assembly.
 13. A ducted electrical power conversion system, comprising: a converter comprising a converter circuitry for converting AC power to DC power and a converter heat sink for cooling the converter circuitry; a first structural duct assembly configured to sealingly receive the converter with the converter heat sink extending into a converter cooling duct channel of the first structural duct assembly, wherein the first structural duct assembly is capable of supporting the converter when the first structural duct assembly is displaced without removal of the converter from the first structural duct assembly; an inverter comprising a inverter circuitry configured to convert DC power from the converter, or other DC feed, to controlled frequency AC power and an inverter heat sink for cooling the inverter circuitry; and a second structural duct assembly mated to the first structural duct assembly and configured to sealingly receive the inverter with the inverter heat sink extending into an inverter cooling duct channel of the second structural duct assembly, wherein the second structural duct assembly is capable of supporting the inverter when the second structural duct assembly is displaced without removal of the inverter from the second structural duct assembly.
 14. The system of claim 13, wherein the first and second structural duct assemblies are capable of supporting the inverter and the converter when the first and second structural duct assemblies are lifted together for displacement without removal of the converter from the first structural duct assembly and without removal of the inverter from the second structural duct assembly.
 15. The system of claim 13, wherein each of the first and second structural duct assemblies includes a respective partition separating the converter and inverter cooling duct channels into separate first and second air channels.
 16. The system of claim 15, wherein the first air channel defined by the respective partition directs cooling air past the inverter, without cooling the inverter, into contact with the converter heat sink.
 17. The system of claim 16, wherein the second air channel defined by the respective partition directs cooling air into contact with the inverter heat sink and past the converter, without cooling the converter.
 18. The system of claim 15, comprising a guide vane adjacent to a base of one of the partitions for controlling flow of cooling air through the first and second air channels.
 19. The system of claim 18, wherein the guide vane is disposed adjacent to an inlet air duct in which a blower directs air into the first and second structural duct assemblies.
 20. A ducted electrical power conversion system, comprising: a converter comprising converter circuitry for converting AC power to DC power and a converter heat sink for cooling the converter circuitry; a first structural duct assembly configured to sealingly receive the converter with the converter heat sink extending into a converter cooling air channel of the first structural duct assembly, wherein the first structural duct assembly is capable of supporting the converter when the first structural duct assembly is displaced without removal of the converter from the first structural duct assembly; an inverter comprising inverter circuitry configured to convert DC power from the converter, DC feed, or common bus, to controlled frequency AC power and an inverter heat sink for cooling the inverter circuitry; a second structural duct assembly mated to the first structural duct assembly and configured to sealingly receive the inverter with the inverter heat sink extending into an inverter cooling air channel of the second structural duct assembly, wherein the second structural duct assembly is capable of supporting the inverter when the second structural duct assembly is displaced without removal of the inverter from the second structural duct assembly; first and second partitions disposed in the first and second structural duct assemblies, respectively, for separating the converter and inverter cooling air channels into separate first and second air channels; first and second baffled walls in the first and second structural duct assemblies, respectively, for directing cooling air into contact with the converter heat sink and the inverter heat sink, respectively; an inlet air duct disposed adjacent to the second structural duct assembly for directing cooling air from a blower into the first and second air channels; and a guide vane adjacent to the inlet air duct for controlling flow of cooling air through the first and second air channels. 